Gas Sensing Device with a Gas Filter

ABSTRACT

A gas sensing device includes chemoresistive gas sensing elements, wherein a material composition of a first chemoresistive gas sensing element is similar to a material composition of a second chemoresistive gas sensing element, wherein the first chemoresistive gas sensing element is exposed to an ambient mixture of gases so that first sensing signals depend on a concentration of a first gas and on a concentration of a second gas, wherein the gas sensing device includes a gas filter so that the second sensing signals depend on the concentration of the first gas to a lesser degree than the first sensor signals and so that the second sensing signals depend on the concentration of the second gas, and wherein the gas sensing device estimates the concentration of the first gas and/or the concentration of the second gas based on the first sensing signals and the second sensing signals.

This application is a continuation of U.S. patent application Ser. No.17/643,653, filed on Dec. 10, 2021, which claims the benefit of EuropeanPatent Application No. 21153058, filed on Jan. 22, 2021, eachapplication being hereby incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to gas sensing devices, in particular tochemoresistive gas sensing devices for sensing different gases in anambient mixture of gases.

BACKGROUND

Chemoresistive sensing devices of sensing different gases are known inthe art. However, there is a need for improving the accuracy of thesensing results of such sensing devices.

SUMMARY

The problem is solved by a gas sensing device for sensing a first gasand at least one second gas in an ambient mixture of gases;

-   -   wherein the gas sensing device comprises a plurality of        chemoresistive gas sensing elements, wherein a first        chemoresistive gas sensing element of the plurality of        chemoresistive gas sensing elements is configured for providing        first sensing signals, and wherein a second chemoresistive gas        sensing element of the plurality of chemoresistive gas sensing        elements is configured for providing second sensing signals;    -   wherein a material composition of the first chemoresistive gas        sensing element is similar to a material composition of the        second chemoresistive gas sensing element, wherein the material        composition is suitable for sensing the first gas and the at        least one second gas;    -   wherein the first chemoresistive gas sensing element is exposed        to the ambient mixture of gases so that the first sensing        signals depend on a concentration of the first gas in the        ambient mixture of gases and on a concentration of the second        gas in the ambient mixture of gases;    -   wherein the gas sensing device comprises a gas filter, which is        less permeable for the first gas than for the at least one        second gas, wherein the gas filter is arranged in such way that        the second chemoresistive gas sensing element is exposed to a        filtered mixture of gases obtained by filtering the ambient        mixture of gases with the gas filter so that the second sensing        signals depend on the concentration of the first gas in the        ambient mixture of gases to a lesser degree than the first        sensor signals and so that the second sensing signals depend on        the concentration of the second gas in the ambient mixture of        gases;    -   wherein the gas sensing device is configured for estimating the        concentration of the first gas in the ambient mixture of gases        and/or the concentration of the second gas in the ambient        mixture of gases based on the first sensing signals and based on        the second sensing signals.

In general, a chemoresistive gas sensing element is an electroniccomponent that changes its electrical resistance in response to changesof the concentrations of nearby gases. The gases, for which achemoresistive gas sensing element is sensitive, depend on the materialcomposition of the chemoresistive gas sensing element. One problem liesin that most of the suitable material compositions interact with morethan one gas, which is also known as cross-sensitivity, so that it isdemanding to distinguish the influence of different gases in a mixtureof gases on the electrical resistance of the chemoresistive gas sensingelement.

The proposed gas sensing device comprises at least a firstchemoresistive gas sensing element for producing first sensing signalsand the second chemoresistive gas sensing element for producing secondsensing signals, wherein the material composition of both chemoresistivegas sensing elements is similar control and in such way that thematerial composition is sensitive to at least a first gas and the secondgas. Each of the gas sensing elements may be manufactured as amicroelectromechanical system (MEMS). The two sensing elements may havesimilar dimensions and may be arranged inside a common package.

The first chemoresistive gas sensing element is arranged in such way,that it is exposed to an ambient mixture of gases comprising at leastthe first gas and the second gas. In contrast to that, the secondchemoresistive gas sensing element is arranged in such way that it isexposed to a filtered mixture of gases which is obtained by filteringthe ambient mixture of gases, wherein the gas filter is used which isimpermeable for the first gas and permeable for the second gas.

In this way, it ensured that the first sensing signals depend on aconcentration of the first gas in the ambient mixture of gases and on aconcentration of the second gas in the ambient mixture of gases.Moreover, it ensured that the second sensing signals do not depend onthe concentration of the first gas in the ambient mixture of gases, orat least to a lesser degree than the first sensor signals. However, thatthe second sensing signals depend on the concentration of the second gasin the ambient mixture of gases.

The gas sensing device estimates the concentration of the first gas inthe ambient mixture of gases and/or the concentration of the second gasin the ambient mixture of gases by taking into account the first sensingsignals and the second sensing signals simultaneously.

The gas sensing device may comprise a processing device comprising a gasconcentration estimator, wherein the first sensing signals and thesecond sensing signals are fed to the gas concentration estimator,wherein the gas concentration estimator is configured for estimating theconcentration of the first gas in the ambient mixture of gases and/orthe concentration of the second gas in the ambient mixture of gasesbased on the first sensing signals and based on the second sensingsignals.

Both of the sensing elements may be controlled by the same processingdevice.

In some embodiments, the processing device comprises hardware only. Inother embodiments, the processing device comprises hardware andsoftware. In particular, the processing device may comprise anapplication-specific integrated circuit (ASIC) and/or a microcontroller.

The gas concentration estimator may comprise the lookup table to whichvalues of the first sensing signals and corresponding values of thesecond sensing signals are fed to, and which outputs values for aconcentration of the first gas and values for concentration of thesecond gas. The content of the lookup table may be determinedexperimentally.

The combination of the first chemoresistive sensing element, the secondchemoresistive sensing element, the gas filter and the estimation of thegas concentrations by assessing simultaneously the first sensor signalsand the second sensor signals ensures that the cross-sensitivity of theproposed gas sensing device is significantly lower than thecross-sensitivity of pre-known multi-gas sensors.

The gas sensing device according to the disclosure is, in particular,suitable for air quality monitoring in outdoor applications. It may beproduced at low costs, may have small dimensions and may have a lowpower consumption.

According to some embodiments, the second chemoresistive gas sensingelement is arranged in an enclosed containment, wherein the gas filteris implemented as a portion of a wall structure of the enclosedcontainment. These features are especially advantages, if the materialof the gas filter does not allow attaching the gas filter directly tothe second chemoresistive gas sensing element. Using an enclosedcontainment ensures that the second chemoresistive gas sensing elementis prevented from getting into contact with the first gas.

According to some embodiments, the first gas is ozone. According to someembodiments, the at least one second gas comprises nitrogen dioxide.Ozone and nitrogen dioxide cause a very similar reaction onchemoresistive gas sensing elements. Thus, prior art chemoresistive gassensor devices are not able to separate completely the contribution ofthe two gases to the eventual value of the electrical resistance of thechemoresistive gas sensing element, as both gases are oxidizing gaseswith similar binding energy causing a similar change in the electricalresistance of the chemoresistive sensing element. However, at thedisclosed solution data the processing device use the information comingfrom the two sensor elements (one exposed just to ozone and the otherexposed to nitrogen dioxide and ozone) to differentiate between the twogases so that it is possible to predict the concentration of each ofthem with high accuracy.

According to some embodiments, the material composition of the firstchemoresistive gas sensing element and of the second chemoresistive gassensing element comprises a mixed oxide (MOX) or materials comprisingcarbon like e. g. graphene, carbon nanotubes etc. Such materials aresuitable for gas sensing devices, however with materials shows strongcross-sensitivity when exposed to nitrogen dioxide and ozone so that itis very demanding to separate properly the contribution of the two gasesto the value of the electrical resistance of the gas sensing elementcomprising these materials. However, the proposed gas sensing device iscapable of measuring correctly the concentration of each of the twogases.

According to some embodiments, the gas sensing device comprises aprocessing device comprising a gas concentration estimator comprising atrained model based algorithm processor having an input layer and anoutput layer, wherein first sensing data derived from the first sensingsignals and second sensing data derived from the second sensing signalsare fed simultaneously to the input layer, and wherein the concentrationof the first gas in the ambient mixture of gases and/or theconcentration of the second gas in the ambient mixture of gases areestimated based on output data of the output layer.

A trained model based algorithm processor is a processor, which iscapable of machine learning. The machine learning is done in apreoperational training phase in which trained models are developed bycomparing actual output values of the trained model based algorithmstage with desired output values of the trained model based algorithmstage for defined inputs of the trained model based algorithm stage. Thetrained models have a predefined structure, wherein a parametrization ofthe predefined structure is done during the training phase. The trainedmodels comprise the learned content after the training phase isfinished. In an operational phase for producing sensing results one ormore of the trained models from the training phase are used to processthe first sensing data and the second sensing data.

In the training phase, a plurality of trained models can be establishedand afterwards stored at the processing device or alternatively on asoftware running on an external microcontroller. The trained models maydiffer in the structures and/or the parameters. During an operationalphase, the most appropriate trained model may be selected depending onthe specific use-case.

The use of a trained model based algorithm processor (in contrast to theuse of a look-up table) ensures, that in an operational phase also inputvalues, which were not used in a pre-operational experimental ortraining phase, are processed in such way that a measurement error isminimized.

According to some embodiments, the first chemoresistive gas sensingelement, the second chemoresistive gas sensing element and theprocessing device are arranged at a common substrate. By these features,the dimensions of the gas sensing device and the manufacturing effortmay be minimized. The common substrate maybe made, in particular, of asemiconductor material.

According to some embodiments, the first chemoresistive gas sensingelement and the second chemoresistive gas sensing element are arrangedin an enclosed housing, wherein a wall structure of the enclosed housingcomprises a particle filter, which is impermeable for particles andpermeable for the first gas and for the at least one second gas. Bythese features, clogging of the gas sensitive areas of the two gassensing elements by particles may be prevented.

According to some embodiments, the gas filter is implemented as acoating of a gas-sensitive area of the second chemoresistive gas sensingelement. The coating may, e.g., comprise manganese oxide (MnO2). Bythese features, the dimensions of the gas sensing device and themanufacturing effort may be further minimized.

According to some embodiments, the gas sensing device comprises a firstheating device configured for heating the first chemoresistive gassensing element and a second heating device configured for heating thesecond chemoresistive gas sensing element, wherein the processing devicecomprises a heat control device configured for controlling the firstheating device according to a first temperature profile and forcontrolling the second heating device according to a second temperaturedevice, wherein a maximum temperature of the first temperature profileis lower than a maximum temperature of the second temperature profile.

In general, the exposure to very high concentrations of oxidizing gases,such as ozone, using high operating temperatures can damage, dependingon the sensing material, the chemoresistive gas sensing elements andusing low operating temperature causes a slow response and recovery ofthe chemoresistive gas sensing elements. Vice versa, the usage of a lowoperation temperature reduces the damage of the chemoresistive sensorelements in presence of oxidizing gases, such as ozone, however a verylow operation temperature is limiting the sensor performance since itcauses a slow sensor response and its subsequent recovery.

As the second chemoresistive gas sensing element of the proposed gassensing device is prevented from contact with one of the gases, theoperational temperatures of the second chemoresistive gas sensingelement may be chosen higher than the operational temperatures of thefirst chemoresistive gas sensing element, in case that the respectivegas is an oxidizing gases such as ozone. In this way, the response andthe recovery of the second chemoresistive gas sensing element can bedrastically enhanced.

According to some embodiments, the first chemoresistive gas sensingelement and the second chemoresistive gas sensing element are arrangedat a common side of the common substrate, wherein the processing deviceis arranged at an opposite side of the common substrate, wherein thefirst chemoresistive gas sensing element and the second chemoresistivegas sensing element are electrically connected to the processing deviceby vias. By these features, the dimensions of the gas sensing device andthe manufacturing effort may be further minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are subsequently discussed withrespect to the accompanying drawings, in which:

FIG. 1 illustrates a first embodiment of a gas sensing device accordingto the disclosure in a schematic cross-sectional top view;

FIG. 2 illustrates the first embodiment of a gas sensing deviceaccording to the disclosure in a schematic cross-sectional side view;

FIG. 3 illustrates a second embodiment of a gas sensing device accordingto the disclosure in a schematic cross-sectional top view;

FIG. 4 illustrates the second embodiment of a gas sensing deviceaccording to the disclosure in a schematic cross-sectional side view;

FIG. 5 illustrates the third embodiment of a gas sensing deviceaccording to the disclosure in a schematic cross-sectional side view;

FIGS. 6A and 6B illustrate an exemplary resistance change of achemoresistive gas sensing element upon applying various concentrationsof nitrogen dioxide and ozone with (FIG. 6A) and without (FIG. 6B) a gasfilter; and

FIG. 7 illustrates an exemplary resistance change of a chemoresistivegas sensing element when applying a certain NO2 concentration measuredsubsequently with different recovery temperatures.

Equal or equivalent elements or elements with equal or equivalentfunctionality are denoted in the following description by equal orequivalent reference numerals.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 illustrates a first embodiment of a gas sensing device 1according to the disclosure in a schematic cross-sectional top view andFIG. 2 illustrates the first embodiment of a gas sensing device 1according to the disclosure in a schematic cross-sectional side view.

Disclosed is a gas sensing device for sensing a first gas and at leastone second gas in an ambient mixture of gases;

-   -   wherein the gas sensing device 1 comprises a plurality of        chemoresistive gas sensing elements 2, 3, wherein a first        chemoresistive gas sensing element 2 of the plurality of        chemoresistive gas sensing elements 2, 3 is configured for        providing first sensing signals S1, and wherein a second        chemoresistive gas sensing element 3 of the plurality of        chemoresistive gas sensing elements 2, 3 is configured for        providing second sensing signals S2;    -   wherein a material composition of the first chemoresistive gas        sensing element 2 is similar to a material composition of the        second chemoresistive gas sensing element 3, wherein the        material composition is suitable for sensing the first gas and        the at least one second gas;    -   wherein the first chemoresistive gas sensing element 2 is        exposed to the ambient mixture of gases so that the first        sensing signals S1 depend on a concentration of the first gas in        the ambient mixture of gases and on a concentration of the        second gas in the ambient mixture of gases;    -   wherein the gas sensing device 1 comprises a gas filter 4, which        is less permeable for the first gas than for the at least one        second gas, wherein the gas filter 4 is arranged in such way        that the second chemoresistive gas sensing element 3 is exposed        to a filtered mixture of gases obtained by filtering the ambient        mixture of gases with the gas filter 4 so that the second        sensing signals S2 depend on the concentration of the first gas        in the ambient mixture of gases to a lesser degree than the        first sensor signals S1 and so that the second sensing signals 2        depend on the concentration of the second gas in the ambient        mixture of gases;    -   wherein the gas sensing device 1 is configured for estimating        the concentration of the first gas in the ambient mixture of        gases and/or the concentration of the second gas in the ambient        mixture of gases based on the first sensing signals S1 and based        on the second sensing signals S2.

According to some embodiments, the second chemoresistive gas sensingelement 3 is arranged in an enclosed containment 5, wherein the gasfilter 4 is implemented as a portion of a wall structure 6 of theenclosed containment 5.

In the example of FIGS. 1 and 2 , the enclosed containment 5 is formedby the gas filter 4, the wall structure 6 and the common substrate 9.

According to some embodiments, the first gas is ozone.

According to some embodiments, the at least one second gas comprisesnitrogen dioxide.

According to some embodiments, the material composition of the firstchemoresistive gas sensing element 2 and of the second chemoresistivegas sensing element 3 comprises a mixed oxide or materials comprisingcarbon like e. g. graphene, carbon nanotubes etc.

According to some embodiments, the gas sensing device 1 comprises aprocessing device 7 comprising a gas concentration estimator 8comprising a trained model based algorithm processor having an inputlayer and an output layer, wherein first sensing data derived from thefirst sensing signals S1 and second sensing data derived from the secondsensing signals S2 are fed simultaneously to the input layer, andwherein the concentration of the first gas in the ambient mixture ofgases and/or the concentration of the second gas in the ambient mixtureof gases are estimated based on output data of the output layer.

According to some embodiments, the first chemoresistive gas sensingelement 2, the second chemoresistive gas sensing element and theprocessing device 7 are arranged at a common substrate 9.

According to some embodiments, the first chemoresistive gas sensingelement 2 and the second chemoresistive gas sensing element 3 arearranged in an enclosed housing wherein a wall structure ii of theenclosed housing 10 comprises a particle filter 12, which is impermeablefor particles and permeable for the first gas and for the at least onesecond gas.

In the example of FIGS. 1 and 2 , the enclosed housing 10 is formed bythe common substrate 9, the wall structure 11 and the particle filter12.

In the example of FIGS. 1 and 2 , the first chemoresistive gas sensorelement 2 comprises one gas sensitive area 13 and the secondchemoresistive gas sensor element 3 comprises one gas sensitive area 14.The first sensing signals S1 are transmitted over first electricalconnectors is from the first chemoresistive gas sensing element 2 to theprocessing device 7. Similarly, the second sensing signals S2 aretransmitted over second electrical connectors 16 from the secondchemoresistive gas sensing element 3 to the processing device 7.

In the example of FIGS. 1 and 2 , the gas sensing device 1 comprises twochemoresistive gas sensing elements 2, 3 with the same type of materialcomposition and controlled by the same processing device 7. Each of thechemoresistive gas sensing elements 2, 3 has one or multiple gas sensingareas 13, 14. All the chemoresistive gas sensing elements 2, 3 arelocated inside the same package and one (or more) of the chemoresistivegas sensing elements 2, 3 is protected by a gas filter 4, which filtersout ozone. The two (or more) chemoresistive gas sensing elements 2, 3can be on different microelectromechanical systems and then thechemoresistive gas sensing element 3 with the gas filter 4 will have anenclosed containment 5 with a wall structure 6 (e.g., a small lid with abig opening) that will mechanically support the gas filter for on top.The chemo resistive gas sensing element 2 without the gas filter 4 willreact to nitrogen dioxide and ozone and should be operated at atemperature low enough in order to avoid oxidation of the material dueto the presence of ozone. The chemoresistive gas sensing element 3 withthe gas filter 4 will not react to ozone and, therefore, is sensitivefor nitrogen dioxide only.

FIG. 3 illustrates a second embodiment of a gas sensing device 1according to the disclosure in a schematic cross-sectional top view andFIG. 4 illustrates the second embodiment of a gas sensing device 1according to the disclosure in a schematic cross-sectional side view.

According to some embodiments, the gas filter 4 is implemented as acoating of a gas-sensitive area 14 of the second chemoresistive gassensing element 3.

According to some embodiments, the gas sensing device 1 comprises afirst heating device 17 configured for heating the first chemoresistivegas sensing element 2 and a second heating device 18 configured forheating the second chemoresistive gas sensing element 3, wherein theprocessing device 7 comprises a heat control device 19 configured forcontrolling the first heating device 17 according to a first temperatureprofile and for controlling the second heating device 18 according to asecond temperature device, wherein a maximum temperature of the firsttemperature profile is lower than a maximum temperature of the secondtemperature profile.

In the example of FIGS. 3 and 4 , the first chemoresistive gas sensingelement 2 is heated by a first heating device 17 and the secondchemoresistive gas sensing element 3 is heated by a second heatingdevice 18. The processing device 7 comprises a heat control device 19,which supplies a first electrical energy E1 over third electricalconnectors 22 the first heating device 17, and which supplies secondelectrical energy E2 over the fourth electrical connectors 23 to thesecond heating device 18. By these features, an operational temperatureof the first chemoresistive gas sensing element 2 may be controlledindependently from an operational temperature of the secondchemoresistive gas sensing element 3. In other embodiments, a commonheating device could be used for heating both of the gas sensingelements 2, 3.

In the example of FIGS. 3 and 4 , both gas sensing elements 2, 3 arearranged on a common microelectromechanical system. The gas sensingelement 3 has a layer of material which catalyzes the ozonedecomposition (e.g., MnO2) deposited or grown on the top of the sensingmaterial.

The gas sensing elements 2, 3 can have independent heating devices 17,18 or just one heating device.

FIG. 5 illustrates the third embodiment of a gas sensing device 1according to the disclosure in a schematic cross-sectional side view.

According to some embodiments, the first chemoresistive gas sensingelement 2 and the second chemoresistive gas sensing element 3 arearranged at a common side of the common substrate 9, wherein theprocessing device 7 is arranged at an opposite side of the commonsubstrate 9, wherein the first chemoresistive gas sensing element 2 andthe second chemoresistive gas sensing element 3 are electricallyconnected to the processing device by vias 22, 23, 24, 25.

In the example of FIG. 5 , the first chemoresistive gas sensing element2 and the second chemoresistive gas sensing element 3 are arranged at atop side of the common substrate 9, wherein the processing device 7 isarranged at a bottom side of the common substrate 9. The first sensingsignals S1 are transmitted over a first group of vias 22 to theprocessing device 7. The second sensing signals are transmitted over asecond group of vias 23 to the processing device 7. The first electricalenergy E1 is provided to the first heating device 17 using a third groupof vias 24. Similarly, the second electrical energy E2 is provided tothe second heating device 18 using a fourth group of wires 25.

The gas sensing device 1 could be extended to other gases which cause asimilar response in the material composition of the gas sensingelements, using two (or more) second chemoresistive gas sensing elements3, where one (or more) of the second chemoresistive gas sensing elements3 is covered with a gas filter for filtering out a first gas of thegases and the other second chemoresistive gas sensing element free (orsensors) has a gas filter for filtering out a further gas of the gases.

FIGS. 6A and 6B illustrate an exemplary resistance change of achemoresistive gas sensing element 2, 3 upon applying variousconcentrations of nitrogen dioxide and ozone with (FIG. 6A) and without(FIG. 6B) a gas filter 4.

The same measurement was done with the same chemoresistive sensingelement 2, 3 twice—once without a gas filter 4 and once with a gasfilter 4. The gas filter 4 was consisting of a standard filter paperwhich was impregnated with indigo—a material which decomposes ozone. Thesensor response to ozone (measured by a change of the resistance of thegas sensitive area 13, 14) is very low when using a gas filter 4 as canbe observed in FIG. 6A. Moreover, the recovery of the chemoresistivesensing element 2, 3 is faster and the damage on the chemoresistivesensing element 2, 3 (resistance increase of the baseline resembling anoxidation of the sensing material) is lowered.

FIG. 7 illustrates an exemplary resistance change of a chemoresistivegas sensing element 2, 3 when applying a certain NO2 concentrationmeasured subsequently with different recovery temperatures.

When the chemoresistive sensing element 3 is protected from exposure tohigh concentration of ozone, then a higher operational temperature canbe used without damaging the chemoresistive sensing element 3. Thiswould improve the overall sensor performance of the secondchemoresistive sensing element 3, thanks to a faster response andrecovery and a more stable reaction to gases. The slightly lowersensitivity at higher temperature is not a limitation since thesensitivity is still above the detection limit for the concentration ofinterest (>20 ppb) of the target gas.

Using 200° C. as recovery temperature results in a more pronouncedsensitivity but the response time as well as the recovery time arelonger compared to a measurement with 300° C. recovery temperature.

Although some aspects have been described in the context of anapparatus, it is clear that these aspects also represent a descriptionof the corresponding method, where a block or device corresponds to amethod step or a feature of a method step. Analogously, aspectsdescribed in the context of a method step also represent a descriptionof a corresponding block or item or feature of a correspondingapparatus.

The above described is merely illustrative, and it is understood thatmodifications and variations of the arrangements and the detailsdescribed herein will be apparent to others skilled in the art. It isthe intent, therefore, to be limited only by the scope of the impendingclaims and not by the specific details presented by way of descriptionand explanation above.

1.-11. (canceled)
 12. A gas sensing device for sensing a first gas andat least one second gas in an ambient mixture of gases; a gas filterthat is less permeable for the first gas than for the at least onesecond gas; a plurality of chemoresistive gas sensing elementsincluding: a first chemoresistive gas sensing element of the pluralityof chemoresistive gas sensing elements configured for providing firstsensing signals, wherein the first chemoresistive gas sensing element isexposed to the ambient mixture of gases so that the first sensingsignals depend on a concentration of the first gas in the ambientmixture of gases and on a concentration of the second gas in the ambientmixture of gases; and a second chemoresistive gas sensing element of theplurality of chemoresistive gas sensing elements configured forproviding second sensing signals, the gas filter arranged so the secondsensing signals depend on the concentration of the first gas in theambient mixture of gases to a lesser degree than the first sensingsignals, and the second sensing signals depend on the concentration ofthe second gas in the ambient mixture of gases, and the gas sensingdevice configured for estimating at least one of the concentration ofthe first gas in the ambient mixture of gases or the concentration ofthe second gas in the ambient mixture of gases based on the firstsensing signals and based on the second sensing signals; an enclosedcontainment including a wall structure, the second chemoresistive gassensing element being arranged in the enclosed containment and the gasfilter being implemented as a portion of the wall structure of theenclosed containment, the wall structure of the enclosed containmentbeing between the first chemoresistive gas sensing element and thesecond chemoresistive gas sensing element; and an enclosed housingincluding a wall structure, the first chemoresistive gas sensing elementand the second chemoresistive gas sensing element being arranged in theenclosed housing, wherein a wall structure of the enclosed housingincludes a particle filter impermeable for particles and permeable forthe first gas and for the at least one second gas.
 13. The gas sensingdevice of claim 12, wherein a material composition of the firstchemoresistive gas sensing element is similar to a material compositionof the second chemoresistive gas sensing element, wherein the materialcomposition is suitable for sensing the first gas and the at least onesecond gas.
 14. The gas sensing device of claim 12, wherein the gasfilter is less permeable for the first gas than for the at least onesecond gas.
 15. The gas sensing device of claim 12, wherein the firstchemoresistive gas sensing element is exposed to the ambient mixture ofgases so that the first sensing signals depend on a concentration of thefirst gas in the ambient mixture of gases and on a concentration of thesecond gas in the ambient mixture of gases.
 16. The gas sensing deviceof claim 12, wherein the gas filter is arranged to expose the secondchemoresistive gas sensing element to a filtered mixture of gasesobtained by filtering the ambient mixture of gases with the gas filterso the second sensing signals depend on the concentration of the firstgas in the ambient mixture of gases to a lesser degree than the firstsensing signals, and the second sensing signals depend on theconcentration of the second gas in the ambient mixture of gases.
 17. Thegas sensing device of claim 12, wherein the first gas is ozone.
 18. Thegas sensing device of claim 12, wherein the at least one second gascomprises nitrogen dioxide.
 19. The gas sensing device of claim 12,wherein a material composition of the first chemoresistive gas sensingelement and of the second chemoresistive gas sensing element comprises amixed oxide or materials comprising carbon.
 20. The gas sensing deviceof claim 12, wherein the gas filter is implemented as a coating of agas-sensitive area of the second chemoresistive gas sensing element. 21.A gas sensing system, comprising; a gas filter that is less permeablefor a first gas than for at least one second gas; a plurality ofchemoresistive gas sensing elements including: a first chemoresistivegas sensing element of the plurality of chemoresistive gas sensingelements configured for providing first sensing signals, wherein thefirst chemoresistive gas sensing element is exposed to the ambientmixture of gases so that the first sensing signals depend on aconcentration of the first gas in the ambient mixture of gases and on aconcentration of the second gas in the ambient mixture of gases; and asecond chemoresistive gas sensing element of the plurality ofchemoresistive gas sensing elements configured for providing secondsensing signals, the gas filter arranged so the second sensing signalsdepend on the concentration of the first gas in the ambient mixture ofgases to a lesser degree than the first sensing signals, and the secondsensing signals depend on the concentration of the second gas in theambient mixture of gases, and the gas sensing device configured forestimating at least one of the concentration of the first gas in theambient mixture of gases or the concentration of the second gas in theambient mixture of gases based on the first sensing signals and based onthe second sensing signals; an enclosed containment including a wallstructure, the second chemoresistive gas sensing element being arrangedin the enclosed containment and the gas filter being implemented as aportion of the wall structure of the enclosed containment, the wallstructure of the enclosed containment being between the firstchemoresistive gas sensing element and the second chemoresistive gassensing element; an enclosed housing including a wall structure, thefirst chemoresistive gas sensing element and the second chemoresistivegas sensing element being arranged in the enclosed housing, wherein awall structure of the enclosed housing includes a particle filterimpermeable for particles and permeable for the first gas and for the atleast one second gas; and a processing device including a gasconcentration estimator having a trained model based algorithm processorwith an input layer and an output layer, wherein first sensing dataderived from the first sensing signals and second sensing data derivedfrom the second sensing signals are fed simultaneously to the inputlayer, and wherein the concentration of at least one of the first gas inthe ambient mixture of gases or the concentration of the second gas inthe ambient mixture of gases are estimated based on output data of theoutput layer.
 22. The gas sensing system of claim 21, wherein the firstchemoresistive gas sensing element, the second chemoresistive gassensing element and the processing device are arranged at a commonsubstrate.
 23. The gas sensing system of claim 21 further comprising: afirst heating device configured for heating the first chemoresistive gassensing element; a second heating device configured for heating thesecond chemoresistive gas sensing element; and a heat control device inthe processing device, the heat control device configured forcontrolling the first heating device according to a first temperatureprofile and for controlling the second heating device according to asecond temperature device, wherein a maximum temperature of the firsttemperature profile is lower than a maximum temperature of a secondtemperature profile.
 24. The gas sensing system of claim 22, wherein thefirst chemoresistive gas sensing element and the second chemoresistivegas sensing element are arranged at a common side of the commonsubstrate, wherein the processing device is arranged at an opposite sideof the common substrate, wherein the first chemoresistive gas sensingelement and the second chemoresistive gas sensing element areelectrically connected to the processing device by vias.
 25. The gassensing system of claim 21, wherein the first gas is ozone, the at leastone second gas comprises nitrogen dioxide, and wherein a materialcomposition of the first chemoresistive gas sensing element and of thesecond chemoresistive gas sensing element comprises a mixed oxide ormaterials comprising carbon
 26. The gas sensing system of claim 21,wherein the first chemoresistive gas sensing element is exposed to theambient mixture of gases so the first sensing signals depend on aconcentration of the first gas in the ambient mixture of gases and on aconcentration of the second gas in the ambient mixture of gases.
 27. Amethod, comprising: exposing a first chemoresistive gas sensing elementto an ambient mixture of a first gas and at least one second gas tocause the first chemoresistive gas sensing element to provide firstsensing signals that depend on a concentration of the first gas in theambient mixture of gases and on a concentration of the second gas in theambient mixture of gases; filtering the ambient mixture of the first gasand at least one second gas with a gas filter to provide a filteredmixture of gases; exposing the second chemoresistive gas sensing elementto the filtered mixture of gases to cause the second chemoresistive gassensing element to provide second sensing signals, the second sensingsignals depending on the concentration of the first gas in the ambientmixture of gases to a lesser degree than the first sensing signals andthe second sensing signals depending on the concentration of the secondgas in the ambient mixture of gases; estimating a concentration of atleast one of the first gas in the ambient mixture of gases or theconcentration of the second gas in the ambient mixture of gases based onthe first sensing signals and based on the second sensing signals;arranging the gas filter, as a portion of a wall structure of anenclosed containment, between the first chemoresistive gas sensingelement and the second chemoresistive gas sensing element; and arrangingthe first chemoresistive gas sensing element and the secondchemoresistive gas sensing element in an enclosed housing having a wallstructure including a particle filter that is impermeable for particlesand permeable for the first gas and for the at least one second gas. 28.The method of claim 27 further comprising coating a gas-sensitive areaof the second chemoresistive gas sensing element to form the gas filter.29. The method of claim 27 further comprising: heating the firstchemoresistive gas sensing element according to a first temperatureprofile; and heating the second chemoresistive gas sensing elementaccording to a second temperature profile, a maximum temperature of thefirst temperature profile being lower than a maximum temperature of asecond temperature profile.
 30. The method of claim 27 furthercomprising: deriving first sensing data from the first sensing signals;deriving second sensing date from the second sending signals; providingsimultaneously the first sensing data and the second sensing data to aninput layer of a trained model based algorithm processor; and estimatingthe concentration of at least one of the first gas in the ambientmixture of gases or the concentration of the second gas in the ambientmixture of gases based on output data provided from an output layer ofthe trained model based algorithm processor.
 31. The method of claim 27,wherein each of the first and second chemoresistive gas sensing elementscomprises a microelectromechanical system (MEMS) structure.